Valacyclovir is safe and effective for treatment of localized herpes zoster in immunocompromised patients 18 years of age and older. This is a randomized, double-blind, controlled trial comparing the efficacy and safety of two doses of oral valacyclovir HCl for the treatment of uncomplicated herpes zoster in immunocompromised patients 18 years of age and older. In order that 25 patients complete therapy and follow-up in each of the two treatment groups, 66 patients will be equally randomized to each of these two treatment groups. Administration of the first dose(day 1) of study drug must occur within 72 hours of zoster rash onset. Patients will receive 1000 mg or 2000 mg valacyclovir three times daily for 7 days. These drugs will be taken orally. Patients' participation will be for a total of 24 weeks. Patients will be seen and assessed for zoster-associated pain and/or abnormal sensations and zoster complications on days 1,3,6,8,10,14,21, and 28 and then every 4 weeks up to and including week 24. Responses to resource use and quality of life questions will be collected at intervals during the study. Safety will be monitored by means of routine hematological and biochemical assessments and reporting of adverse experiences.